DS1874T+ Maxim Integrated Products, DS1874T+ Datasheet - Page 12

• Manufacturer Part Number: DS1874T+
• Description: IC CTLR SFP+ ANLG LDD 28-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Controllerr

Specifications of DS1874T+

• Number Of Channels: 1
• Voltage - Supply: 2.85 V ~ 3.9 V
• Current - Supply: 2.5mA
• Operating Temperature: -40°C ~ 95°C
• Package / Case: 28-WFQFN Exposed Pad
• Mounting Type: Surface Mount
• Number Of Outputs: 5
• Duty Cycle (max): 50 %
• Output Voltage: 0 V to 3.9 V
• Mounting Style: SMD/SMT
• Switching Frequency: 0 KHz to 400 KHz
• Operating Supply Voltage: 2.85 V to 3.9 V
• Supply Current: 2.5 mA to 10 mA
• Maximum Operating Temperature: + 95 C
• Fall Time: 300 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 300 ns
• Synchronous Pin: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 90-1874T+000

The DS1874 integrates the control and monitoring func-
tionality required to implement a VCSEL-based SFP or
SFP+ system using Maxim’s MAX3798/MAX3799 com-
bined limiting amplifier and laser driver. Key compo-
nents of the DS1874 are shown in the Block Diagram
and described in subsequent sections.
The DS1874 controls two 9-bit DACs inside the
MAX3798/MAX3799. One DAC is used for laser bias
SFP+ Controller with Digital LDD Interface
12
______________________________________________________________________________________
MAX3798/MAX3799 DAC Control
100Ω
+3.3V
Detailed Description
R
BD
VCSEL-TOSA
PIN-ROSA
R
MON
BMON
MON1
MON2
MON3
3W
3W
LA
LDD
MAX3798/MAX3799
DS1874
EEPROM
control while the other is used for laser modulation con-
trol. The DS1874 communicates with the MAX3798/
MAX3799 over a 3-wire digital interface (see the 3-Wire
Master for Controlling the MAX3798/MAX3799 section).
The communication between the DS1874 and
MAX3798/MAX3799 is transparent to the end user.
The MAX3798/MAX3799 control their laser bias current
DAC using the APC loop within the DS1874. The APC
loop’s feedback to the DS1874 is the monitor diode
(MON2) current, which is converted to a voltage using
QUICK
MODE
TRIP
ADC
LOS
BIAS
DAC
DAC
RSELOUT
I
DISABLE
TXDOUT
2
LOSOUT
C
FAULT
RSEL
RSEL
LOS
TXD
SDA
SCL
LOS
TXF
Typical Operating Circuit
BIAS Register/APC Control
TX_FAULT
TX_DISABLE
MODE_DEF2 (SDA)
MODE_DEF1 (SCL)
RATE SELECT
LOS